Double stroller...necessary?

Need advice from moms of 2... do you use a double stroller often? I have a 2 year old and baby due in March and I'm struggling to justify the price of a double stroller with car seat adapter. My son often wants to walk, but he does still go in the stroller for longer walks, the zoo, festivals, etc.

I was also thinking I could use a baby carrier for the newborn and small umbrella stroller for my 2 year old to travel lighter. Advice? Thanks!